Saved searches
A saved search is a search you can run again, and an alert that watches for new properties matching it. You do not get one without the other: saving is switching it on.
What gets saved
Three things, and they do different jobs.
The name is for you. Name it for why you saved it. "Kreuzberg, two bed, under 600" tells you something in three months; "Search 3" does not.
The words are what alerts compare new properties against. This is the part that does the work, and the part people leave empty because the filters felt like enough. See alerts for why that matters.
The filters are what you had set at the moment you saved: the district you added while exploring, the price ceiling from before you changed your mind. They are restored when you re-run the search. Look at them before saving, because they are captured as they stand rather than as you remember them.
Wording one
Write the sentence you would say to somebody who knows the market.
Quiet two-bedroom flat in Kreuzberg or Neukölln, balcony or terrace, up to about 600,000, ready to move into.
That has a place, a size, a thing that matters to you, a rough budget and a condition. Every one of those gives an arriving property something to be compared against.
Compare it with "2 bed Berlin", which describes several thousand properties and will alert on most of them.
Two habits are worth avoiding:
Do not restate the filters in words. "City: Berlin. Bedrooms: 2. Price: 600000" reads as a form rather than a description, and matches accordingly.
Do not describe a property that does not exist. A sentence with nine requirements in it will match nothing and will never say so. If you would compromise on something, leave it out.
Several narrow beats one wide
Two specific searches are better than one loosened to cover both.
You can tell at a glance which one fired. You can delete one without touching the other. And each stays specific enough to be worth reading, which the combined one would not be.
A common pair: one for the flat you actually want at the price you would pay, and a second, wider one on the same area at a higher ceiling, to find out whether your ceiling is realistic. The second is not really an alert; it is a way of learning the market without opening the site every day.
Filters worth knowing about
Most filters do what they say. Two do something you would not expect.
Living area is the most-omitted useful field on a listing. Filtering on it removes every property whose agent left it blank, which in some markets is a third of them. If a search returns far less than you expected, this is usually why.
A map area is drawn rather than typed, and it beats a district name when the thing you care about is a walk rather than an administrative boundary.
Re-running one
Re-running restores the filters and the words together. If you have since changed your mind about the budget, change it and save a new search rather than editing your way across several sessions: the alert compares against the words that were stored when it was saved.
When to delete one
When you have bought, when you have moved on, or when it has become a search you scroll past. An alert you ignore is worse than none, because it teaches you to ignore the next one.
Deleting is the only way to stop an alert. There is no pause. See alerts.